How to 404 Redirect Deleted Tag Pages?

I recently deleted about 150 tags on my health website, because google does not want us covering “sexual health” topics. In Google Webmaster tools I now have a warning that all of the deleted tag pages are not returning 404 messages, so I checked it out and lo and behold the deleted tag pages are not returning 404 messages. How can I set these deleted tag pages (like websitename.com/tag/gonorrhea/ ) to return 404 error messages?

there are two ways one is that leave these warning as it is and after few months google will remove those.
other is install a plugin for 301 redirect and add all the tags urls and redirect to pages on which you want.

Davidjoseph doesn’t complain Google is still display these tag pages as indexed content… He complains that his website don’t return the 404 error as it’s usually the case if the tag doesn’t exist anymore.

So that means there is a deeper problem on his wordpress installation / theme.

sorry for not reading properly I thought this question similar to previous post which complain about GWT.
” I now have a warning that all of the deleted tag pages are not returning 404 messages,”
I am not sure about this what he mean i never seen any message on GWT.
but my solution will still work for him

What difference would this make? If these template files aren’t present in the theme, then any call to a tag age would fall back – eventually – to index.php as outlined in the Theme Template Hierarchy.